One aspect of our proposal is concerned with the coupling of human red cell glycolysis to the membrane Na,K-ATPase responsible for cation transport. The experimental method that we have primarily employed is 31p nuclear magnetic resonance. We propose to use this method to study the following questions: 1) the mechanism of cardiac glycoside action on alkali cation transport with emphasis on cardiac glycoside specificity; 2) the role of glyceraldehyde 3-phosphate dehydrogenase in modulating cation transport; (3) the extent of the glycolytic enzyme complex in red cell cytoplasm; 4) the relation between the integral membrane protein, Band 3, and the membrane Na,K-ATPase; and 5) the nature of coupling within the red cell with emphasis on: an understanding of how so few copies of membrane Na,K-ATPase can propagate their interactions so effectively to many times more copies of other red cell proteins as well as an understanding of how the glycolytic enzyme complex is attached to the cell membrane. Another aspect of the proposal deals with the study of Ca interactions using the Eigen type temperature-jump apparatus to study kinetics in the microsecond range. We propose to investigate: 1) the fast kinetics of interaction of Ca with the Ca ionophore, A 23187; 2) the fast kinetics of the reaction of Ca with purified sarcoplasmic reticulum vesicles containing only the membrane bound Ca,Mg-ATPase; and 3) the kinetics of Ca binding to the red cell membrane Ca sites by a method which permits identification of the individual processes on each face of the cell membrane.